diff --git a/eel/eel-vfs-extensions.c b/eel/eel-vfs-extensions.c
index d007b5fb0e570289036ec863fd0b2f691d71e1b2..1c4b5b1155446faa13293c9f8cd6bac22e5af04e 100644
--- a/eel/eel-vfs-extensions.c
+++ b/eel/eel-vfs-extensions.c
@@ -33,8 +33,9 @@
 
 #include "eel-string.h"
 
-#include <string.h>
+#include <ctype.h>
 #include <stdlib.h>
+#include <string.h>
 
 /**
  * eel_filename_get_extension_offset:
@@ -65,6 +66,14 @@ eel_filename_get_extension_offset (const char *filename)
         return NULL;
     }
 
+    for (size_t i = 1; end[i] != '\0'; i += 1)
+    {
+        if (isspace (end[i]))
+        {
+            return NULL;
+        }
+    }
+
     if (end != start)
     {
         if (strcmp (end, ".gz") == 0 ||
diff --git a/src/nautilus-file-operations.c b/src/nautilus-file-operations.c
index c20cf895efa92f8f47fc670d7bbfd65bb69ce574..1faa1ae4142292d663d70be9a75dfbea20619547 100644
--- a/src/nautilus-file-operations.c
+++ b/src/nautilus-file-operations.c
@@ -9358,7 +9358,8 @@ nautilus_self_check_file_operations (void)
     EEL_CHECK_STRING_RESULT (get_duplicate_name ("foo foo", 1, -1, FALSE), "foo foo (copy)");
     EEL_CHECK_STRING_RESULT (get_duplicate_name ("foo.txt", 1, -1, FALSE), "foo (copy).txt");
     EEL_CHECK_STRING_RESULT (get_duplicate_name ("foo foo.txt", 1, -1, FALSE), "foo foo (copy).txt");
-    EEL_CHECK_STRING_RESULT (get_duplicate_name ("foo foo.txt txt", 1, -1, FALSE), "foo foo (copy).txt txt");
+    EEL_CHECK_STRING_RESULT (get_duplicate_name ("foo foo.txt txt", 1, -1, FALSE), "foo foo.txt txt (copy)");
+    EEL_CHECK_STRING_RESULT (get_duplicate_name ("foo foo.txt txt (copy)", 1, -1, FALSE), "foo foo.txt txt (another copy)");
     EEL_CHECK_STRING_RESULT (get_duplicate_name ("foo...txt", 1, -1, FALSE), "foo.. (copy).txt");
     EEL_CHECK_STRING_RESULT (get_duplicate_name ("foo...", 1, -1, FALSE), "foo... (copy)");
     EEL_CHECK_STRING_RESULT (get_duplicate_name ("foo. (copy)", 1, -1, FALSE), "foo. (another copy)");